Many attempts have been made to prepare hybrid polymer dispersions, in particular alkyd-acrylic hybrid polymer dispersions, aiming to achieve an ideal balance of the best properties of each of the polymers combined in the hybrid polymer. Alkyd emulsions and acrylic dispersions, made by means of emulsion polymerization, are the two most common waterborne technologies used in the coating industry. Coatings based on alkyd emulsions exhibit advantages over those based on acrylic dispersions in terms of gloss, brush-ability, open time, flow and levelling, hiding per coat, mar resistance, sand-ability, and adhesion. Advantages of acrylic dispersions over alkyd emulsions include quick drying, durability, non-yellowing, non-embrittling, and non-chalking (pigment release by degradation of the binder).
In addition to the advantages described above for alkyds, coatings based on alkyd-modified hybrid dispersions have improved film forming properties due to the presence of alkyd moieties, which typically have a low glass transition temperature (Tg). However, the presence of the alkyd also results in critical problems, such as soft films (causing dirt pick-up and poor block resistance), high residual vinyl monomer content and yellowing. High residual monomer content is a threat to the environment and health and is strictly regulated. Furthermore, during the addition polymerisation, unsaturated groups on the alkyd are lost, resulting in the deterioration of the auto-oxidation properties of the alkyd. The known hybrids also have an undesirably low open time, defined as the period of time during which corrections can be made in the wet paint film without leaving brush marks.